It is already known from DE-A-37 17 975 for brittle material for grinding to be crushed in the gap between two rollers which are pressed against one another at high pressure, wherein a part-stream of the comminuted material for grinding is returned to the roller gap and is further comminuted together with fresh material for grinding. In this connection the problem has arisen of satisfactorily comminuting material for grinding with a high moisture content which above a critical moisture value has a strong tendency to sticking end/or caking. In order to achieve this, at least a proportion of the part-stream returned to the roller gap is dried before re-introduction into the roller gap to such an extent that a mixed moisture content occurs in the roller gap which lies below the critical moisture content, and in this came the so-called "boundary moisture content" above which the material for grinding has a strong tendency to sticking and/or caking is taken to be 12%, so that a moisture content of somewhat below this value is sought. If the moisture content is regarded as too low then an artificial increase in the mixed moisture content is considered advantageous.
The object of the invention is to provide a method and apparatus with a reliable and relatively easily controllable mode of operation which ensures a particularly good capacity for drawing in brittle material for grinding, particularly sand-like brittle material for grinding, into the roller gap between two rollers of a material bed roller mill.